perf tools: Make fetch_kernel_version() publicly available

There are 2 places in llvm-utils.c which find kernel version information
through uname. This patch extracts the uname related code into a
fetch_kernel_version() function and puts it into util.h so it can be
reused.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1446818135-87310-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

3 files changed, 49 insertions, 33 deletions

diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index 8ee25bea1b24..00724d496d38 100644
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -4,7 +4,6 @@
  */
 
 #include <stdio.h>
-#include <sys/utsname.h>
 #include "util.h"
 #include "debug.h"
 #include "llvm-utils.h"
@@ -216,18 +215,19 @@ static int detect_kbuild_dir(char **kbuild_dir)
         const char *suffix_dir = "";
 
         char *autoconf_path;
-        struct utsname utsname;
 
         int err;
 
         if (!test_dir) {
-                err = uname(&utsname);
-                if (err) {
-                        pr_warning("uname failed: %s\n", strerror(errno));
+                /* _UTSNAME_LENGTH is 65 */
+                char release[128];
+
+                err = fetch_kernel_version(NULL, release,
+                                           sizeof(release));
+                if (err)
                         return -EINVAL;
-                }
 
-                test_dir = utsname.release;
+                test_dir = release;
                 prefix_dir = "/lib/modules/";
                 suffix_dir = "/build";
         }
@@ -325,38 +325,18 @@ get_kbuild_opts(char **kbuild_dir, char **kbuild_include_opts)
         pr_debug("include option is set to %s\n", *kbuild_include_opts);
 }
 
-static unsigned long
-fetch_kernel_version(void)
-{
-        struct utsname utsname;
-        int version, patchlevel, sublevel, err;
-
-        if (uname(&utsname))
-                return 0;
-
-        err = sscanf(utsname.release, "%d.%d.%d",
-                     &version, &patchlevel, &sublevel);
-
-        if (err != 3) {
-                pr_debug("Unablt to get kernel version from uname '%s'\n",
-                         utsname.release);
-                return 0;
-        }
-
-        return (version << 16) + (patchlevel << 8) + sublevel;
-}
-
 int llvm__compile_bpf(const char *path, void **p_obj_buf,
                       size_t *p_obj_buf_sz)
 {
+        size_t obj_buf_sz;
+        void *obj_buf = NULL;
         int err, nr_cpus_avail;
-        char clang_path[PATH_MAX], nr_cpus_avail_str[64];
+        unsigned int kernel_version;
         char linux_version_code_str[64];
         const char *clang_opt = llvm_param.clang_opt;
-        const char *template = llvm_param.clang_bpf_cmd_template;
+        char clang_path[PATH_MAX], nr_cpus_avail_str[64];
         char *kbuild_dir = NULL, *kbuild_include_opts = NULL;
-        void *obj_buf = NULL;
-        size_t obj_buf_sz;
+        const char *template = llvm_param.clang_bpf_cmd_template;
 
         if (!template)
                 template = CLANG_BPF_CMD_DEFAULT_TEMPLATE;
@@ -388,8 +368,11 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
         snprintf(nr_cpus_avail_str, sizeof(nr_cpus_avail_str), "%d",
                  nr_cpus_avail);
 
+        if (fetch_kernel_version(&kernel_version, NULL, 0))
+                kernel_version = 0;
+
         snprintf(linux_version_code_str, sizeof(linux_version_code_str),
-                 "0x%lx", fetch_kernel_version());
+                 "0x%x", kernel_version);
 
         force_set_env("NR_CPUS", nr_cpus_avail_str);
         force_set_env("LINUX_VERSION_CODE", linux_version_code_str);
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index cd12c25e4ea4..47b1e36c7ea0 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -3,6 +3,7 @@
 #include "debug.h"
 #include <api/fs/fs.h>
 #include <sys/mman.h>
+#include <sys/utsname.h>
 #ifdef HAVE_BACKTRACE_SUPPORT
 #include <execinfo.h>
 #endif
@@ -665,3 +666,32 @@ bool find_process(const char *name)
         closedir(dir);
         return ret ? false : true;
 }
+
+int
+fetch_kernel_version(unsigned int *puint, char *str,
+                     size_t str_size)
+{
+        struct utsname utsname;
+        int version, patchlevel, sublevel, err;
+
+        if (uname(&utsname))
+                return -1;
+
+        if (str && str_size) {
+                strncpy(str, utsname.release, str_size);
+                str[str_size - 1] = '\0';
+        }
+
+        err = sscanf(utsname.release, "%d.%d.%d",
+                     &version, &patchlevel, &sublevel);
+
+        if (err != 3) {
+                pr_debug("Unablt to get kernel version from uname '%s'\n",
+                         utsname.release);
+                return -1;
+        }
+
+        if (puint)
+                *puint = (version << 16) + (patchlevel << 8) + sublevel;
+        return 0;
+}
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 4cfb913aa9e0..2665126267dc 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -350,4 +350,7 @@ static inline char *asprintf_expr_not_in_ints(const char *var, size_t nints, int
 
 int get_stack_size(const char *str, unsigned long *_size);
 
+int fetch_kernel_version(unsigned int *puint,
+                         char *str, size_t str_sz);
+
 #endif /* GIT_COMPAT_UTIL_H */